1. Field of the Invention
The present invention relates to a liquid cooled floodlight fixture in which the cooling device is provided with a method of shedding atmospheric moisture which condenses on the cooling device so that condensed moisture is restrained from coming into contact with and damaging moisture vulnerable floodlight fixture components.
2. Description of Prior Art
Heat is a major cause of shortened lamp life, particularly in sodium vapor lamps where heat forces the excess sodium-mercury mixture into the arc tube current raising the voltage across the lamp thereby increasing material decomposition in the lamp which shortens the lamp's working lifespan. Heat radiated by a high wattage lamp also increases the temperature in an enclosed area, such as the area contained in a greenhouse or film studio. A liquid cooled floodlight fixture can collect and transfer radiated lamp heat via the liquid transfer medium to a location external to the areas where ambient temperature conditions are desired. The heated liquid transfer medium can be cooled by a refrigeration device or by an evaporative cooling device and the liquid transfer medium can be recycled back through the floodlight cooling device to reabsorb additional radiated heat. If water is used as a heat transfer medium, the heated water can be expelled down a drain and a continuous supply of fresh water can be introduced into the floodlight cooling apparatus to remove radiated heat from the lamp.
In greenhouses a high relative humidity can exist. The high humidity condition causes water vapor from the atmosphere to condense and form water droplets on the surfaces of the floodlight cooling device. Water droplets can also form and collect between closely spaced heat collecting fins used in some types of cooling devices and can reduce the overall effective heat absorbing surface area of the cooling device. If some area of the cooling device is located in a space directly above a vulnerable electrical component, such as the optimum heat absorbing area directly above a hot gloss envelope of the lamp, water droplets falling on the hot glass envelope of the lamp can fracture the glass envelope and destroy the lamp. Other problems encountered with dripping water inside a floodlight fixture include electrical shorts, mildew, rot and rusting of lamp components.
Other applications for use of a moisture shedding liquid cooled floodlight fixture include farming operations conducted inside space stations, space vehicles and undersea dwellings.
Originally, floodlight fixtures designed to dissipate excess heat radiated by a lamp were intended only to extend the operating life of the lamp. The additional cost of manufacturing many heat dissipating floodlight fixture outweighted the economic advantages of extending the operating life of the lamp. However, in a greenhouse application, liquid cooled light fixtures have multiple advantages. Among the advantages of a liquid cooled light fixture in a greenhouse is the ability to provide a closed, ambient temperature condition that maintains a constant ratio of carbon dioxide to air in a carbon dioxide enriched greenhouse by eliminating the need for air conditioning or excessive ventilation. Other advantages include producing a controlled, closed environment free of insect pests, mold and fungus that can damage greenhouse plants; reducing radiated heat from lamps so that more lamps can be used within a confined area to more closely duplicate the luminosity of the outdoor sunlight; and enabling a greenhouse operator to position a liquid cooled floodlight closer to living greenhouse plants producing greater luminosity at closer light source distances with the same electricity consumption while eliminating the problems of overheating, scorching and drying out the plants. Prior art such as U.S. Pat. No. 4,598,347 issued to Peppers (1986) dissipated electric lamp heat into the immediate surrounding atmosphere which in an enclosed area created the need for ventilation or air conditioning. Prior art that involved encapsulating an electric lamp in a transparent water jacket had the disadvantage of substantially reducing the luminosity of the light fixture as well as creating the possibility of a short circuit if water were to leak into the lamp socket. The liquid cooled light fixture disclosed in U.S. Pat. No. 1,457,646 issued to Wilson (1926), was a metal, water jacketed light fixture which was unsuitable for greenhouse applications because it focused light from a lamp bulb and created a hot spot at the point of focus. The Wilson light fixture was inefficient in that it had a limited surface area for heat absorption, was expensive to manufacture, had poor internal reflectivity, and had no means to shed condensed moisture. Prior art involving a lamp containing within it a means of cooling had the disadvantage of being expensive to manufacture and expensive to replace. The internal lamp cooling surfaces also decreased lamp luminosity. In addition, all liquid cooled floodlight fixtures heretofore known suffer from one or more of a number of disadvantages:
(a) There has been no consideration given to controlling and eliminating condensed water vapor from the atmosphere that condenses on the surfaces of the cooling device creating the problems encountered when moisture comes into contact with various moisture vulnerable components of the floodlight fixture.
(b) Floodlight fixtures heretofore have been designed with cooling devices that restrict light ray divergence because of the physical presence of the cooling device which obstructs the widest possible divergence of light rays.
(c) Cooling devices in floodlight fixtures have been designed in such a way that they reduce the luminosity of the lamp or the luminosity is reduced by physical obstructions to the light emitted by the lamp.
(d) Floodlight fixtures with cooling devices reflect the lamp light in such a way that portions of the light rays become focused creating a hot spot that impinges on plants and burns the plant at that point.
(e) No consideration has been given to the problem of eliminating condensed water retention between heat exchanger cooling fins in a light fixture.
(f) Cooling devices in light fixtures have heretofore been designed to fit a specific floodlight fixture precluding the use of a compact, universal design for the cooling device which can be retrofitted to a wide variety of different floodlight fixtures.